When two persons are talking, it requires a certain amount of ‘processing power’ of a hearing impaired third person to distinguish between the voices of the two persons and to separate the two sound sources, if they overlap in time. It is especially demanding, if it is not possible for the hearing impaired person to observe the mouths of the talking persons (to practice lip reading). Similar problems may arise in noisy environments where (e.g. normally hearing) persons wear ear-protection devices that (in a specific mode of operation) allow the reception of selected parts of the surrounding sound field.
In a typical hearing instrument comprising a directional microphone system (beamformer), a standard directional mode of operation (DIR mode) is provided to focus a characteristic of the microphone system on the sound sources (to provide maximum gain (minimum attenuation) in a direction of the target sound source(s), cf. illustration on FIG. 1A. FIG. 1A shows a standard reaction of a (two-microphone) hearing instrument to focus listening in a given direction, i.e. to listen to two persons talking, where both instruments of a binaural hearing system are focused on both talkers (at the same time) meaning they will receive almost the same sound mix at each ear.